The Role of Potential Flow in the Theory of the Navier-Stokes Equations

2009 ◽  
pp. 311-317
Author(s):  
Daniel D. Joseph
Keyword(s):  
Potential Flow ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Navier Stokes Equations

Numerical Investigation of the Effect of Balancing-Hole on the Axial Force of a Partial Emission Pump

2014 ◽  
Author(s):  
Zhang Lisheng ◽  
Jiang Jin ◽  
Xiao Zhihuai ◽  
Li Yanhui
Keyword(s):  
Axial Force ◽  
Stokes Equations ◽  
Dominant Role ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Design Parameters ◽  
Navier Stokes Equations ◽  
Computational Fluid Dynamics Cfd ◽  
The Cost

In this paper numerical simulations were conducted to analyze the effects of design parameters and distribution of balancing-hole on the axial-force of a partial emission pump. The studied pump is a single stage pump with a Barske style impeller. Based on the original impeller, we designed 7 pumps with different balancing-hole diameters and the partial emission pump equipped with different impellers were simulated employing the commercial computational fluid dynamics (CFD) software Fluent 12.1 to solve the Navier-Stokes equations for three-dimensional steady flow. A sensitivity analysis of the numerical model was performed with the purpose of balancing the contradiction of numerical accuracy and the cost of calculation. The results showed that, with increasing of the capacity, the axial force varies little. The diameter of the inner balancing-hole plays a dominant role of reducing axial-force of partial emission pump, the axial-force decreases with increasing of inner balancing-hole diameter on the whole range of operation, the axial-force of impeller without inner balancing-hole is approximately 3 times larger than that of impeller with inner balancing-hole. While the diameter of outer balancing-hole has a reverse effects compared with that of inner balancing-hole. With increasing of outer balancing-hole, the axial force increases accordingly.

Scouring Below Pipelines: The Role of Vorticity and Turbulence

2010 ◽  
Author(s):  
Matteo Mattioli ◽  
Alessandro Mancinelli ◽  
Giuseppina Colicchio ◽  
Maurizio Brocchini
Keyword(s):  
Numerical Model ◽  
Lift Force ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Offshore Pipeline ◽  
Temporal Averaging ◽  
Force Components

A numerical study on the turbulence and vorticity of local scour underneath an offshore pipeline placed on a non-cohesive sandy seabed and forced by a steady flow current is presented. The numerical model solves the Navier-Stokes equations using an innovative Level Set technique. The model predicts the behavior of the movable sediments through both drift and lift force components. Mean and turbulent flow quantities were extracted by temporal averaging. Results on the distribution and evolution of turbulent kinetic energy and vorticity will be illustrated at the conference.

scholarly journals Competition between Chaotic Advection and Diffusion: Stirring and Mixing in a 3D Eddy Model

2018 ◽  
Author(s):  
Genevieve Jay Brett ◽  
Larry Pratt ◽  
Irina Rypina ◽  
Peng Wang
Keyword(s):  
Turbulent Diffusion ◽  
Stokes Equations ◽  
Effective Diffusivity ◽  
Eddy Diffusivity ◽  
Chaotic Advection ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Spatially Varying ◽  
Future Work

Abstract. The importance of chaotic advection relative to turbulent diffusion is investigated in an idealized model of a 3D swirling and overturning ocean eddy. Various measures of stirring and mixing are examined in order to determine when and where chaotic advection is relevant. Turbulence is alternatively represented by: 1) an explicit, observation–based, scale–dependent eddy diffusivity, 2) stochastic noise, added to a deterministic velocity field, or 3) explicit and implicit diffusion in a spectral numerical model of Navier–Stokes equations. Lagrangian chaos in our model occurs only within distinct regions of the eddy, including a large chaotic ‘sea’ that fills much of the volume near the perimeter and central axis of the eddy, and much smaller ‘resonant’ bands. The size and distribution of these regions depends on factors such as the degree of axial asymmetry of the eddy and the Ekman number. The relative importance of chaotic advection and turbulent diffusion within the chaotic regions is quantified using three measures: the ratio of the tracer filament arrest scale to the width of the chaotic region, the rate of dispersal of closely spaced fluid parcels, and the Nakamura effective diffusivity. The role of chaotic advection in the stirring of a passive tracer is generally found to be most important within the larger chaotic ‘seas’, at intermediate times, with small diffusivities, and for eddies with strong asymmetry. In contrast, in thin chaotic regions, turbulent diffusion at oceanographically relevant rates is at least as important as chaotic advection. Future work should address anisotropic and spatially–varying representations of turbulence for more realistic models.

Convective Heat Transfer in Turbulent Flow Near a Gap

2006 ◽  
Vol 128 (7) ◽  
pp. 701-708 ◽  
Author(s):  
D. Chang ◽  
S. Tavoularis
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Large Scale ◽  
Stokes Equations ◽  
Reynolds Stress Model ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Vortical Structures

Convective heat transfer in a rectangular duct containing a heated rod forming a narrow gap with a plane wall has been simulated by solving the unsteady Reynolds-averaged Navier-Stokes equations with a Reynolds stress model. Of particular interest is the role of quasi-periodic coherent structures in transporting fluid and heat across the gap region. It is shown that the local instantaneous velocity and temperature vary widely because of large-scale transport by coherent vortical structures forming in pairs on either side of the rod.

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